Seed plant

A seed plant or spermatophyte is any plant that makes seeds. These plants are very important because most of the plants we see around us, like trees, shrubs, and flowers, are seed plants. They include the flowering plants and the gymnosperms, but not plants like ferns, mosses, or algae.

The word phanerogam means "visible" in Ancient Greek. It is used to describe plants that have visible parts for making seeds, unlike some other plants that have hidden parts for this purpose. Seed plants have special ways of growing and spreading, which helps them live in many different places on Earth.

Description

Seed plants are plants that make seeds. They include most plants you see around you, like trees and flowers. There are five main groups of seed plants alive today.

Four groups are called gymnosperms, meaning their seeds are not covered. These groups are:

• Cycadophyta, the cycads, which grow in warm areas
• Ginkgophyta, which has just one type of tree left today
• Pinophyta, the conifers, trees and bushes that carry cones
• Gnetophyta, a small group of woody plants

The fifth group is the flowering plants, also called angiosperms. They are the biggest and most varied group of seed plants. Their seeds are inside a fruit, which is different from gymnosperms.

We also know about many seed plants that no longer exist from fossils. One early group was called "seed ferns". They were common in ancient forests during a time called the Paleozoic. Another important ancient tree was Glossopteris, which grew in a place called Gondwana long ago.

Evolutionary history

Main article: Evolutionary history of plants § Seeds

Seed plants began to evolve when their ancestors went through a big change in their genes about 319 million years ago. Scientists found an early example of these plants in Belgium that is about 385 million years old. This plant, called Runcaria, looked very simple and had parts that might have helped it spread its pollen by wind. It was almost a seed plant but did not have a solid seed coat or a way to guide pollen to the seed.

After Runcaria, other plants with more advanced features appeared. By the end of the Devonian period, around 359 million years ago, seed plants had become more diverse and included several different types.

Phylogeny

Seed-bearing plants are a group within the vascular plants. They have special structures that help them carry water and nutrients.

Traditionally, seed plants were split into two main groups: flowering plants and gymnosperms. Gymnosperms include plants like ginkgo, cycads, and conifers. Recent studies show that gymnosperms form a group, with gnetophytes close to conifers. These relationships are still being studied.

Some classifications put all seed plants into one big group, with five smaller groups inside it. Others treat these groups as separate divisions. There are also many extinct orders of seed plants that no longer exist.